1. Field of the Invention
The subject invention relates to a container assembly for mixing materials and in particular for mixing liquid and dry reactants to form bone cement for use in surgical procedures.
2. Description of the Prior Art
It is well known that in many surgical procedures it is necessary to employ a cement or grouting type agent. The type of cement generally used for these procedures is formed of self-curing resins from the blending of a wide variety of liquid monomers or commoners with powdered polymers or copolymers, which forms a viscous mixture. When set, the resulting cements contain ploy (methyacrylic acid esters) as their main ingredient. The solid polymer powder is typically a finely divided air-fluffed powder which can also contain such things as radiopacifiers, antibiotics, plasticizers, crosslinking agents, and compositing reinforcing fibers or beads.
The mixture of the powder and liquid components develops a quick setting material and preparation of the cement usually occurs directly within the operating room just prior to use. The mixing to form the cement typically occurs in a container assembly having a mixing device and a mixing chamber. These type of container assemblies are typically provided in two different forms.
One type of container assembly, which is disclosed in U.S. Pat. No. 4,961,647, includes a mixing bowl having a mixing device. The powder is first placed in the mixing bowl, the liquid component is introduced, and then the mixing device is mounted to the container assembly. After the liquid and powder are mixed to form the cement, the cement can be scooped out of the container assembly with any suitable utensil.
Another type of container assembly, which is disclosed in U.S. Pat. No. 5,265,956, includes a mixing bowl mounted to a cartridge. The mixing bowl also includes a mixing device. The powder is placed into the mixing bowl, the liquid component is introduced, and then the mixing device is mounted to the container assembly. After the liquid and powder are mixed to form the cement, the cement is transmitted into the cartridge. The cartridge is subsequently removed from the container assembly and mounted to an extrusion device.
The container assemblies of the prior art are effective in mixing and delivering the cement. However, there is little development in the prior art regarding the difficulties in introducing the powder to the mixing chamber while ensuring that the powder does not escape from the mixing chamber. As recognized by one skilled in the art, the finely divided air-fluffed powder used in these mixtures has a tendency to escape from the mixing chamber. The discharge of powder is undesirable because of the potential health hazard and the potential to contaminate the operating room. In addition, the escaped powder reduces the amount of cement and can cause an improper mixing ratio between the liquid and the powder, thereby reducing the effectiveness of the powder.
It therefore desirable to pre-pack the mixing chamber with the powder and effectively seal the mixing chamber with a storage cover. It is also desirable to subsequently control the opening of the storage cover from the mixing chamber to reduce or eliminate the discharge of powder.